Go before 1.17 does not properly consider extraneous zero characters at the beginning of an IP address octet, which (in some situations) allows attackers to bypass access control that is based on IP addresses, because of unexpected octal interpretation. This affects net.ParseIP and net.ParseCIDR.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-29923
• golang/go#30999
• golang/go#43389
• https://defcon.org/html/defcon-29/dc-29-speakers.html#kaoudis
• https://github.com/sickcodes/security/blob/master/advisories/SICK-2021-016.md
• https://go-review.googlesource.com/c/go/+/325829/
• https://golang.org/pkg/net/#ParseCIDR
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4CHKSFMHZVOBCZSSVRE3UEYNKARTBMTM/
• https://www.oracle.com/security-alerts/cpujan2022.html
• https://security.gentoo.org/glsa/202208-02